JP2621040B2 - Vertical general purpose internal combustion engine - Google Patents

Description

Description: Object of the Invention (Industrial application field) The present invention relates to an overhead valve type vertical general-purpose internal combustion engine in which a crankshaft is disposed vertically, and more particularly, to supply and exhaust of an air-cooled internal combustion engine. It relates to the improvement of the structure.

(Prior Art) An air-cooled vertical general-purpose internal combustion engine employing an overhead valve type is used as a drive source for working equipment such as a lawn mower and a grass mower for agricultural work and civil engineering work. As this kind of general-purpose internal combustion engine, Japanese Patent Laid-Open Publication No.
There is one disclosed in JP-A-1-116054.

This general-purpose internal combustion engine employs a layout that lowers the overall height of the internal combustion engine in order to improve the stability of the body of the working equipment. For this reason, in the conventional general-purpose internal combustion engine, as shown in FIGS. 10 and 11, the intake and exhaust valves 1 and 2 arranged vertically are formed in an overhead valve system, and the intake passage 3 is formed by the cylinder of the engine cylinder 4. On one side of the head 4a, an exhaust passage 5 is opened on the opposite side. A carburetor 6 and an air cleaner (not shown) forming an engine intake system are arranged in the intake passage 3 in a distributed arrangement in which a muffler 7 is connected to the exhaust passage 5.

(Problems to be Solved by the Invention) In the conventional vertical general-purpose internal combustion engine, since the exhaust valve 2 is arranged below and the intake valve 1 is arranged above the cylinder head 4a of the engine cylinder 4, the exhaust passage 5 Is the intake passage 3
, And the exhaust valve 2 and the exhaust passage 5 are located far from the cooling fan 8. For this reason, the cooling efficiency is poor, the cylinder head 4a is likely to be heated to a high temperature, abnormal combustion such as knocking is likely to occur, and the layout of the carburetor 6 and the like of the engine intake system is set as low as possible. Must be arranged in an upward slope toward the intake valve 1. Moreover, the intake valve 1 is the exhaust valve 2
, The heat of the engine exhaust system is easily transmitted to the intake system to become high temperature, and there is a problem that the output may be reduced due to abnormal combustion due to the heating of the intake air.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a vertical general-purpose internal combustion engine capable of improving combustion performance by improving the cooling performance of a cylinder head and stabilizing combustion.

Another object of the present invention is to improve the intake passage to improve the output by imparting a swirl effect to the intake air, and to lower the position of an engine intake system such as a carburetor. An internal combustion engine is provided.

[Configuration of the invention]

(Means for Solving the Problems) In order to achieve the above object, a vertical general-purpose internal combustion engine according to the present invention is provided with a cooling fan at an upper end portion of a vertically arranged crankshaft, and the fan case has an engine case. In a vertical general-purpose internal combustion engine in which an intake valve and an exhaust valve are disposed in a cylinder head of the engine cylinder in an overhead valve manner, an exhaust valve is positioned above an intake valve in the cylinder head. Each valve is disposed vertically, an intake passage upstream from the intake valve is formed upward, and this intake passage is passed between a pair of push rods respectively driving the intake valve and the exhaust valve. An enlarged portion is formed in the intake passage further upstream from the push rods in the intake passage, and the enlarged portion has an intake gas for closing a part thereof. An inlet is inserted to form an upstream intake passage that is bent downward, and an upstream end of the upstream intake passage is opened to one side wall surface of the cylinder head to connect a carburetor, while an exhaust passage from the exhaust valve is provided. At least the axis of the lower side of the bisector perpendicular to the line connecting the axis of the intake valve and the exhaust valve, and open to the other side wall surface of the cylinder head opposite to the end of the intake passage opening. An exhaust muffler is connected, and a hole for mounting a spark plug is drilled on the exhaust passage side with respect to a line connecting the axis of the intake valve and the exhaust valve and below the exhaust passage.

(Operation) The intake passage has a downstream passage from the downstream end communicating with the intake valve to the vicinity of the push rod facing upward,
Since the upstream passage from the vicinity of the push rod to the intake opening end is bent downward, the swirl flow is generated in the fuel mixture flowing through the bent intake passage, thereby producing a swirl effect. Can be given. As a result, the fuel sucked into the combustion chamber from the intake valve is positively stirred and sucked while turning counterclockwise or clockwise, thereby improving combustion. Also, since the upstream side of the intake passage is bent downward toward the opening end, the high-density fuel sucked from the carburetor of the intake system is swirled while atomizing along the upper wall of the intake passage, and further complete combustion is achieved. It can be further promoted.

Further, since the downstream side passage of the bent intake passage is directed downward toward the intake valve, fuel easily accumulates around the intake valve. For this reason, when the engine is started, the fuel accumulated around the intake valve in the intake passage is sucked into the cylinder and sufficient starting fuel can be supplied, so that the startability can be improved.

Furthermore, since both open ends of the intake and exhaust passages are distributed to the left and right side surfaces of the cylinder head and formed at lower positions on the respective side surfaces, the center of gravity of the engine is lowered in a well-balanced manner on the left and right sides. It is possible to increase the capacity of the air cleaner of the intake system connected to the intake system.

In addition, since the upstream side of the intake passage from the vicinity of the push rod to the intake opening end is turned downward by inserting the intake guide into the straight upwardly expanding portion, the intake passage can be easily formed into a U-shape. Can be bent. That is,
Even if a simple die having a straight upward intake passage is used as the cylinder head casting die, the straight intake passage can be easily bent downward.

Also, by appropriately changing the shape of the intake guide,
The shape of the intake passage can be easily changed.

Furthermore, since the intake passage and the pair of push rods, and the exhaust passage and the hole for mounting the ignition plug are separately arranged on the left and right sides of the cylinder head, the heat generated by the exhaust passage and the ignition plug is provided in the intake passage and the push rod. Heat damage can be effectively prevented.

Hereinafter, an embodiment of a vertical general-purpose internal combustion engine according to the present invention will be described with reference to the accompanying drawings.

FIGS. 1 and 2 are a vertical sectional view and a plan sectional view, respectively, showing a vertical general purpose internal combustion engine according to the present invention employing an overhead valve system. In the drawing, reference numeral 10 denotes a horizontal engine cylinder of a general-purpose internal combustion engine, in which a piston 11 is slidably accommodated. The engine cylinder 10 is integrally or integrally connected to a crankcase 12, while the crankcase 12 has a bearing 13
The crankshaft 14 is disposed vertically via the.
The crankshaft 14 is connected to the piston 11 via a connecting rod 15, and is driven to rotate by driving the piston 11.

The upper end of the crankshaft 14 protrudes upward through the crankcase 12, and a cooling fan 17 is attached to the protruding end. The cooling fan 17 is covered from above by a fan cover 18, and guides cooling air into the fan cover 18. A cooling path (ventilation path) 19 is formed.

On the other hand, the crankshaft 14 protrudes downward from the crankcase 12, and the output can be taken out from the tip thereof.

Further, a cylinder head 21 is provided on a cylinder block 20 of the engine cylinder 10, and the cylinder head 21 is covered with a head cover 22. The cylinder head 21 is provided with an intake valve 23 and an exhaust valve 24 of an overhead valve type. In this case, the exhaust valve 24 is located above the intake valve 23 and is arranged close to the cooling fan 17 side. The intake valve 23 and the exhaust valve 24 are driven to open and close by a cam 25 interlocking with the crankshaft 14 via a push rod 26 and a rocker arm 27, respectively, and are normally biased by a return spring 28 in a direction to close the valve. Is done.

An intake passage 30 is opened on one side of the cylinder head 21. The intake passage 30 passes between the push rods 26 of the intake valve 23 and the exhaust valve 24 as shown in FIG.
It forms a downward slope toward 3. A carburetor 33 and an air cleaner 34 constituting an engine intake system 32 are sequentially connected to the intake passage 30.

On the other hand, an exhaust passage 35 is opened on the opposite side surface of the cylinder head 21 where the intake passage 30 is formed. The exhaust passage 35 is formed with an upward slope toward the exhaust valve 24, while the exhaust passage
An exhaust muffler 36 is connected to 35. The exhaust passage 35 is located above the intake passage 30 in the cylinder head 21 and is formed near the upper wall of the cylinder head 21 at a position close to the cooling fan 17.

With this arrangement, the heat of the engine exhaust system is easily transferred upward and is transferred to the upper wall side of the cylinder head 21, but since this portion is first hit by the cooling air from the cooling fan 17, The cylinder head 21 is effectively cooled, and its heating can be prevented friendly.

At this time, the intake passage 30 is formed downward, and the upper wall side is effectively heated by the exhaust valve 24 and the exhaust passage 35 through which the high-temperature exhaust gas passes. Collision with the wall promotes vaporization,
Complete combustion. The intake passage 30 is a push rod
Although the position is specified to pass between 26 and 26, the exhaust passage 35
Has a high degree of freedom in layout and can be formed in an appropriate direction of the cylinder head 21. Also in this case, since the exhaust valve 24 is installed near the upper wall of the cylinder head 21 and on the cooling fan 17 side, the cooling performance of the cylinder head 21 is not impaired.

The intake passage formed in the cylinder head 21 is the third
Instead of forming straight downward as shown in the figure,
As shown by reference numeral 40 in FIGS. 4 to 8, a curved shape may be used. Since the configuration other than the intake passage 40 of the cylinder head 21 is not different from that shown in FIGS. 1 to 3, the same reference numerals are given and the description is omitted.

In the vertical general-purpose internal combustion engine shown in FIG. 4, a pair of push rods 2 for driving the intake valve 23 and the exhaust valve 24 are formed through an intake passage 40 communicating with the intake valve 23.
An opening is provided on one side of the cylinder head 21 through the space between the cylinders 6 and 26 and connected to the engine intake system 32. The intake passage 40 is disposed so as to be substantially perpendicular to a line aa connecting the axes of the push rods 26, 26, and the push rods 26, 26 are disposed on both radial sides of the intake passage 40.

The exhaust passage 35 from the exhaust valve 24 is connected to the cylinder head 21.
, And is connected to the exhaust muffler 36 on the other side of the cylinder head 21. Exhaust valve 24 and intake valve 23
A hole 45 for mounting a spark plug is formed on the exhaust passage 35 side with respect to a line bb connecting the axes of the above. The mounting hole 45 is provided below the exhaust passage 35 and below a bisector XX orthogonal to a line bb connecting the axis of the intake valve 23 and the exhaust valve 24.

Thus, the intake passage 40 and the pair of push rods 26, 2
6 and the exhaust passage 35 and the spark plug mounting hole 45 are arranged separately on the left and right sides of the cylinder head 21.
Heat damage caused by the heat of the exhaust passage 35 and the ignition plug is effectively prevented from being applied to the intake passage 40 and the push rods 26, 26.

The center line of the intake passage 40 formed in the cylinder head 21 is bent in the shape of a letter or a rectangle between the push rods 26, 26 of the intake / exhaust valves 23, 24, and has an opening on the side of the cylinder head 21. Is formed so as to gradually expand toward. Due to this expansion, the casting of the cylinder head 21 is improved during casting. The intake passage 40 is a gasket (insulator)
The gasket 41 is connected to the carburetor 33 of the engine intake system 32 via 41, and the gasket 41 has an intake hole 42 having a diameter smaller than the enlarged portion 40a of the intake passage 40, and the enlarged portion of the intake passage 40.
A tongue-shaped intake guide 43 inserted into 40a is provided. The intake guide 43 closes a part of the expanded portion 40a of the intake passage 40 and guides the intake air sucked from the carburetor 33 so as to be largely curved in the intake passage 40.

At this time, since the intake passage 40 is greatly curved at the boundaries of the push rods 26, 26, a swirl effect occurs due to the swirling flow, and the fuel sucked from the intake valve 23 into the combustion chamber is counterclockwise (or clockwise). )) While being positively agitated while being swirled and sucked to improve combustion. Also, the intake passage 40
Has a curved downward structure, the high-density fuel sucked from the carburetor 33 is swirled while being atomized along the upper wall of the intake passage 40 to promote complete combustion.

Furthermore, the intake passage 40 is formed in the shape of a triangle, and its expanded portion
When the gasket 41 is interposed in the 40a as shown in FIG. 9, the mounting position of the carburetor 33 can be lowered, and the engine intake system 32 can be lowered by that much, and the center of gravity can be reduced. In addition, the capacity of the air cleaner 34 can be increased. Furthermore, since the gasket 41 having the smaller-diameter intake hole 42 is attached to the large opening of the enlarged portion 40a of the intake passage 40, the degree of freedom in mounting the carburetor 33 increases depending on the intake hole 42 of the gasket 41. Since the upper and lower mounting positions of the carburetor 33 can be adjusted, optimum combustion conditions can be easily obtained.

〔The invention's effect〕

As described above, in the vertical general-purpose internal combustion engine according to the present invention, the intake passage is configured such that the downstream passage from the downstream end communicating with the intake valve to the vicinity of the push rod faces upward, while the intake passage extends from the vicinity of the push rod. Since it is bent so that the upstream passage to the intake opening end faces downward, a swirl flow can be generated in the air-fuel mixture flowing through the bent intake passage to give a swirl effect. . As a result, the fuel sucked into the combustion chamber from the intake valve is positively stirred and sucked while turning counterclockwise or clockwise, thereby improving combustion. Also, since the upstream side of the intake passage is bent downward toward the opening end, the high-density fuel sucked from the carburetor of the intake system is swirled while atomizing along the upper wall of the intake passage, and further complete combustion is achieved. It can be further promoted.

Further, since the downstream side passage of the bent intake passage is directed downward toward the intake valve, fuel easily accumulates around the intake valve. For this reason, when the engine is started, the fuel accumulated around the intake valve in the intake passage is sucked into the cylinder and sufficient starting fuel can be supplied, so that the startability can be improved.

Furthermore, since both open ends of the intake and exhaust passages are distributed to the left and right side surfaces of the cylinder head and formed at lower positions on the respective side surfaces, the center of gravity of the engine is lowered in a well-balanced manner on the left and right sides. It is possible to increase the capacity of the air cleaner of the intake system connected to the intake system.

In addition, since the upstream side of the intake passage from the vicinity of the push rod to the intake opening is turned downward by inserting the intake guide into the straight upwardly expanding portion, the intake passage is easily bent in a U-shape. can do. In other words, even if a simple mold having a straight upward intake passage is used as the cylinder head casting die, the straight intake passage can be easily bent downward.

Also, by appropriately changing the shape of the intake guide,
The shape of the intake passage can be easily changed.

Furthermore, since the intake passage and the pair of push rods, and the exhaust passage and the hole for mounting the ignition plug are separately arranged on the left and right sides of the cylinder head, the heat generated by the exhaust passage and the ignition plug is provided in the intake passage and the push rod. Heat damage can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a vertical general-purpose internal combustion engine according to the present invention, FIG. 2 is a plan sectional view substantially along the line II-II of FIG. 1, and FIG. FIG. 4 is a bottom view of the cylinder head taken along the line III-III, FIG. 4 is a view showing a modification of the cylinder head used in the vertical general-purpose internal combustion engine of the present invention, and FIG. FIG. 6 is a bottom view similar to FIG. 3, FIG. 6 is an external side view of the cylinder head shown in FIG. 4, FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 4, and FIG. FIG. 9 is a cross-sectional view taken along line VIII-VIII of FIG. 9, FIG. 9 is a cross-sectional view showing a gasket interposed in an enlarged portion of an intake passage of a cylinder head, and FIGS. 10 and 11 show a conventional vertical general-purpose internal combustion engine. FIG. 10 ... engine cylinder, 11 ... piston, 12 ... crankcase, 14 ... crankshaft, 17 ... cooling fan, 18 ... fan cover, 19 ... cooling path, 20 ... cylinder block, 21 ...
Cylinder head, 22 ... Head cover, 23 ... Intake valve, 24 ...
Exhaust valve, 26 ... push rod, 30, 40 ... intake passage, 32 ...
Engine intake system, 33 ... carburetor, 34 ... air cleaner,
35 ... Exhaust passage, 40a ... Expansion part, 41 ... Gasket, 43 ... Intake guide.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location F02P 13/00 301 F02P 13/00 301A

Claims (1)

(57) [Claims] 1. A cooling fan is provided at an upper end of a vertically arranged crankshaft, a fan case covers an engine cylinder from above, and an intake valve and an exhaust valve are provided in a cylinder head of the engine cylinder by an overhead valve system. In the arranged vertical general-purpose internal combustion engine, the exhaust valve is located above the intake valve in the cylinder head, and each valve is disposed vertically, and an intake passage upstream from the intake valve is formed upward. Passing the intake passage between a pair of push rods respectively driving the intake valve and the exhaust valve, and forming an enlarged portion in the intake passage further upstream of the push rod in the intake passage, An intake guide that partially closes the intake passage is inserted into the expanded portion to form an upstream intake passage that is bent downward, and the upstream end of the upstream intake passage is connected to a cylinder. While connecting the carburetor by opening it on one side wall of the valve, at least the axis of the exhaust passage from the exhaust valve is defined by a bisector perpendicular to the line connecting the axis of the intake valve and the exhaust valve. An exhaust muffler is connected to the lower side and opened to the other side wall surface of the cylinder head opposite to the intake passage opening end, and the exhaust passage is closer to the exhaust passage than a line connecting the axis of the intake valve and the exhaust valve. A vertical general-purpose internal combustion engine characterized in that a hole for mounting a spark plug is drilled below.